Myelodysplastic Syndromes (MDS) are malignant, potentially fatal blood diseases that arise from a defective hematopoietic stem/progenitor cell. MDS are heterogeneous diseases with few treatment options. One of the key challenges facing MDS treatment is the lack of effective medicines capable of providing a durable response.
MDS are hematologic malignancies defined by blood cytopenias due to ineffective hematopoiesis, and a predisposition to acute myeloid leukemia (AML) (Corey et al., 2007; Nimer, 2008). MDS is most prominent in individuals over 60 years of age, and as a result of longer life expectancies, the incidence of MDS has escalated in recent years (Sekeres, 2010b). MDS is fatal in majority of patients as a result of marrow failure, immune dysfunction, and/or transformation to overt leukemia. Current treatment options for MDS include allogeneic HSC transplantation, demethylating agents, and immunomodulatory therapies (Ebert, 2010). At present, the only curative treatment for MDS is (hemopoeitic stem cell) HSC transplantation, an option unavailable to many of the older patients. Instead, these patients receive supportive care and transfusions to ameliorate their disease complications. Unfortunately, even with this treatment, the MDS clones persist in the marrow and the disease invariably advances (Tehranchi et al., 2010). For advanced disease or high-risk MDS, patients may also receive immunosuppressive therapy, epigenetic modifying drugs, and/or chemotherapy (Greenberg, 2010). Despite recent progress, most MDS patients exhibit treatment-related toxicities or relapse (Sekeres, 2010a). Overall the efficacy of these treatments is variable, and generally life expectancies are only slightly improved as compared to supportive care.
Approximately 30% of MDS patients also develop aggressive Acute Myeloid leukemia (AML) due to acquisition of additional mutations in the defective hematopoietic stem/progenitor cell (HSPC) (Greenberg et al., 1997). AML is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal white blood cells that accumulate in the bone marrow and interfere with the production of normal blood cells. AML is the most common acute leukemia affecting adults, and its incidence increases with age. Although AML is a relatively rare disease, accounting for approximately 1.2% of cancer deaths in the United States, its incidence is expected to increase as the population ages. Several risk factors and chromosomal abnormalities have been identified, but the specific cause is not clear. As an acute leukemia, AML progresses rapidly and is typically fatal within weeks or months if left untreated. The prognosis for AML that arises from MDS has a worse as compared to other types of AML.
Consequently, there is an urgent need to develop targeted therapies capable of eliminating the MDS-initiating clones, and for treatments and method of treating MDS and AML. Identification of molecular targets is essential to improve outcome and eliminate the MDS-causing clones and/or AML. Herein, therapeutic targets and agents for treating MDS and/or AML are described.